Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known foil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
During construction of a wind turbine, rotor blades must be mounted to a hub of the wind turbine. Typically, this mounting is done on-site at the location of the wind turbine, after transporting the various wind turbine components to the location. As the rotor blades, and the wind turbines in general, increase in size and weight, the task of mounting the rotor blades has become increasingly difficult.
One prior art solution for on-site mounting of the rotor blades is to perform the mounting task before lifting and connecting the hub on the wind turbine tower. However, the hub and rotor blades must then be lifted together and connected on the wind turbine tower. Lifting of the combined hub and rotor blades is difficult, expensive, and time consuming, due to the size and weight of the hub and rotor blades.
Another prior art solution for on-site mounting is to connect the hub on the wind turbine tower and then mount each rotor blade to the hub. For example, each individual rotor blade may be hoisted by a crane or suitable hoisting device and mounted to the hub. However, mounting of the rotor blades to the hub in this manner may be dangerous due to, for example, the imbalance created in the wind turbine after installation of only a portion of the rotor blades.
One prior art attempt to reduce the dangers associated with the imbalances created during mounting of the rotor blades has been to lock the brake disk that is provided in the wind turbine adjacent the hub flange, and then unlock and rotate the brake disk as required to position the hub for mounting of the various rotor blades. A locking device is provided to lock the brake disk, and a rotation device is connected to the brake disk to rotate the brake disk as required for mounting of the rotor blades. However, this system has a variety of disadvantages. For example, the rotation device must impart a large force onto the brake disk to rotate the brake disk, and this force increases as rotor blades are mounted to the hub, which increases the load that must be rotated. Further, as the sizes of the hub and rotor blades increase, even greater forces may be required. Existing systems, in order to adequately rotate the brake disk, are thus large and expensive.
Thus, improved methods and apparatus for mounting a rotor blade to a hub are desired in the art. For example, methods and apparatus that require relatively less force to rotate the hub as desired would be advantageous. Additionally, methods and apparatus that are cost-effective would be advantageous. Further, methods and apparatus that may be retrofitted to existing wind turbines would be desired.